It's the image people get of fat people as being lazy and hedonistic. Whether this is true or not, this is how they're viewed.

I don't hate people for being fat. However, I hate when fat people think the world should cater to them because they're fat. No, airlines don't need to make bigger seats just for 400 pound people. And if you squeeze yourself into a seat and spill over into the personal space of the people next to you, they have a right to judge you.